This invention relates to the attachment of separable fastener strip to web substrate, and is especially useful for producing bag-making material in which plastic film carries extruded plastic separable fastener means in strip form.
As revealed in the prior art exemplified by U.S. patents, proposals for uniting extruded separable fasteners, sometimes referred to in the trade as zippers, have comprised joining the fastener profile strips to a compatible extruded synthetic plastic film substrate while both of the separately, but simultaneously extruded components are still in a sufficiently plastic state to fuse together, as exemplified in U.S. Pat. Nos. 3,462,332 ,4,259,133 and Re.29,208.
Another technique, as exemplified in U.S. Pat. Nos. 3,784,432 and 4,279,677, includes joining the freshly extruded profile strips to compatible prefabricated plastic film substrate while the fastener strip is still in a sufficiently thermoplastic state to permit fusing the thermoplastic film which is reheated from a cold state to accelerate the fusion.
A further technique as exemplified in U.S. Pat. No. 3,532,571 includes joining freshly extruded film to compatible prefabricated fastener strips while the film is still in a sufficiently thermoplastic state to permit fusing the fastener strip to the film.
It has, of course, been longtime common practice to join prefabricated fastener strip to prefabricated compatible plastic film by fusion welding, as exemplified in U.S. Pat. No. 3,948,705, and suggested in British Patent No. 1,587,609. This British patent also has a bare suggestion of adhesive attachment of the strip.
A distinct advantage attributable to prefabricating profile fastener strips and bag making plastic film resides in the fact that because of the relatively larger section modulus of the profile strips as compared to the section modulus of the plastic film, the plastic film when extruded separately can be run at a much greater speeds than the profile fastener strips. Therefore, by spooling the prefabricated fastener strips and the prefabricated film in separate rolls, they can be fed simultaneously at desired speed and joined together as by means of adhesive applied in a fluent state between the elements as they are brought convergently together, as exemplified, by U.S. Pat. Nos. 4,101,355; 4,341,575 and 4,355,494. By such prefabrication and then adhesive joinder of the profile fastener strips and the substrate, relatively incompatible materials may be utilized to advantage in the respective elements. For example, a form of plastic material which will lend itself to best advantage for extrusion of the profile strips, and will afford the most advantageous elastic deformation separable coaction of the fastener profiles, may be utilized for that purpose, while materials having special characteristics desirable for the end product such as bags may be utilized in the film whether plastic or non-plastic. The composite finished product will then be endowed with all of the preferred characteristic in both the fastener and the substrate.
With all of the advantages inherent in adhesively securing prefabricated elastically deformable separable profile fastener strips to prefabricated film substrate, there is still room for substantial improvement in the adhesive attachment technique. A disadvantage of adhesive attachment as heretofore proposed has been the requirement for extremely accurate control of the fluent adhesive, both as to volume at point of application, temperature gradients during application, tackiness, machine down time, necessarily close attention to the adhesive applicators, avoidance of adhesive spray machine foul-up, and the like. Therefore, on-site adhesive joinder of the profile fastener strips and the substrate has placed a heavy burden on the machine operators to maintain all of the critical parameters necessary for successful results. This has been particularly the case when the adhesive attachment is combined with a form-fill operation as described in U.S. Pat. No. 4,355,494, where the advantage of shipping finished film and fastener separately and thereby saving space, and the advantage of reducing spool changeover because of the larger spools, are then lost due to the relatively complex adhesive applying operation.
In the copending application of Russell J. Gould, Ser. No. 894,669, now U.S. Pat. No. 4,731,911 filed of even date herewith, and assigned to the same assignee, is disclosed a substantial improvement in supplying web-free fastener strips with reactivatable adhesive.
The disclosure in U.K. patent application No. 2,080,412A suggests that the heat reactivatable adhesive carried by the fastener strips be reactivated by employing the conventional heating and pressing jaws or bars commonly used to weld strips to the synthetic material for bags. This involves a stop and start technique.
The beforementioned U.S. Pat. No. 3,948,705 discloses a welding technique utilizing continuous heat or ultrasonic sealing means whereby side flanges on the fastener strip are welded to the substrate.
In copending U.S. Pat. No. 4,430,070 and 4,601,194 of Steven Ausnit, is disclosed the technique of fusion welding of the plastic film to the fastener strip base by means of hot air or radiant heat.
However, none of the disclosures hereinabove discussed provides method and means for high speed, mass production attachment of web and separable fastener strip from a cold state by means of reactivatable adhesive carried by the fastener strip base.